1) create a moh category called: silence (PBX -> Music On Hold)
2) cp /var/lib/asterisk/sounds/en/silence/9.gsm /var/lib/asterisk/mohmp3/silence/
3) chown asterisk:asterisk /var/lib/asterisk/mohmp3/silence/9.gsm
4) uncomment musiconhold => default on /etc/asterisk/agents.conf and leave it as:
musiconhold => silence
5) asterisk -rx “module reload”
6) login as a call center agent